1. Field of the Invention
The invention relates to a method of recognizing a speech signal, which is derived from coherently spoken words and which consists of a temporal sequence of speech values, each of which indicates a section of the speech signal, the speech values being successively compared with reference values, of which each time a group of reference values represents a word of a given vocabulary and the reference values are derived from phonemes, while each comparison result is added to a minimum distance sum, which was attained with the preceding speech value for reference values lying in a given neighbourhood increased by a time distortion value depending upon the neighbourhood as a new distance sum.
2. Description of the Prior Art
A method of recognizing coherently spoken words is essentially known from DE-OS 32 15 868. In this case, the individual words are built up of sequences of reference values. It is also known to take phonemes into account, for example from Bell System Technical Journal, Vol. 62, No. 4, April 1983, pp. 1035-1075. A phoneme is then represented in simplified form by a single reference value and in a normally spoken phrase several successive speech values then generally go with such a phoneme reference value because the duration of a section of the speech signals, which is represented by a speech value, is normally shorter than a phoneme. The number of times a speech value corresponds to a phoneme reference value is then not taken into account, however, or rather passes into an increase of the distance sum, as a result of which the real speech signal is not optimally valued.